Mega Code Archive
This program demonstrates a list that dynamically computes list entries
<![CDATA[
/*
This program is a part of the companion code for Core Java 8th ed.
(http://horstmann.com/corejava)
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.EventQueue;
import javax.swing.AbstractListModel;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.ListSelectionModel;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.ListSelectionListener;
/**
* This program demonstrates a list that dynamically computes list entries.
* @version 1.23 2007-08-01
* @author Cay Horstmann
*/
public class LongListTest
{
public static void main(String[] args)
{
EventQueue.invokeLater(new Runnable()
{
public void run()
{
JFrame frame = new LongListFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
});
}
}
/**
* This frame contains a long word list and a label that shows a sentence made up from the chosen
* word.
*/
class LongListFrame extends JFrame
{
public LongListFrame()
{
setTitle("LongListTest");
setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);
wordList = new JList(new WordListModel(3));
wordList.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
wordList.setPrototypeCellValue("www");
JScrollPane scrollPane = new JScrollPane(wordList);
JPanel p = new JPanel();
p.add(scrollPane);
wordList.addListSelectionListener(new ListSelectionListener()
{
public void valueChanged(ListSelectionEvent evt)
{
StringBuilder word = (StringBuilder) wordList.getSelectedValue();
setSubject(word.toString());
}
});
Container contentPane = getContentPane();
contentPane.add(p, BorderLayout.NORTH);
label = new JLabel(prefix + suffix);
contentPane.add(label, BorderLayout.CENTER);
setSubject("fox");
}
/**
* Sets the subject in the label.
* @param word the new subject that jumps over the lazy dog
*/
public void setSubject(String word)
{
StringBuilder text = new StringBuilder(prefix);
text.append(word);
text.append(suffix);
label.setText(text.toString());
}
private static final int DEFAULT_WIDTH = 400;
private static final int DEFAULT_HEIGHT = 300;
private JList wordList;
private JLabel label;
private String prefix = "The quick brown ";
private String suffix = " jumps over the lazy dog.";
}
/**
* A model that dynamically generates n-letter words.
*/
class WordListModel extends AbstractListModel
{
/**
* Constructs the model.
* @param n the word length
*/
public WordListModel(int n)
{
length = n;
}
public int getSize()
{
return (int) Math.pow(LAST - FIRST + 1, length);
}
public Object getElementAt(int n)
{
StringBuilder r = new StringBuilder();
;
for (int i = 0; i < length; i++)
{
char c = (char) (FIRST + n % (LAST - FIRST + 1));
r.insert(0, c);
n = n / (LAST - FIRST + 1);
}
return r;
}
private int length;
public static final char FIRST = 'a';
public static final char LAST = 'z';
}
]]>